The River Styx is a location in Dante's Inferno. comprises most of the Fifth Circle. Those damned for the sin of Anger are immersed in this toxic, black liquid that makes up the river. The angry lie at the top, where they attempt to tear one another apart, while the sullen lie at the bottom. Unwary travelers are dragged under by the angry shades. Dante's only way across is the guardian of the Styx, Phlegyas. Beyond Styx lies the gates to the City of Dis. The Tower of Anger also lies at the banks of this river, signaling the boatman.
- In Greek mythology, the River Styx (meaning "Hateful") was one of the five rivers of the Underworld. It has since become the most famous of the five, and has sometimes become synonymous with "the River of Hell". Unlike the Acheron, the Styx had no ferryman, though Charon is often mistakenly placed here in some popular media.
- In the original myths, the Styx was named after its resident nymph, who had saved Zeus from destruction during the Titanomachy. In honor of Styx, he declared her river would be the sacred river on which holy oaths would be sworn. If these oaths were ever broken by a mortal, that mortal would instantly die. If a god broke their oath, they would be placed into a deathlike coma for several months and be maligned upon awakening for breaking their word. Furthermore, as shown in the myth of Achilles, it would seem that a mortal who was bathed in the Styx would be physically invulnerable to any weapons wherever their skin was directly touched by the waters (though as Achilles had been dipped in as an infant by his mother, another nymph, it is unknown if simply bathing in the Styx is all that is needed to make a human invulnerable).
- In "The Inferno", Dante describes how the River Styx made up much of the fifth circle, and within its swampy waters, the souls of both the Wrathful and the Sullen were punished.
- Apparently the Styx is so deep that Phlegyas wades underwater and only the flat top of his crown can be seen.
- Charon's severed head can be found in the Styx marsh, acting as a nest for pests.